Projection optical system, projection apparatus, and projection system

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United States of America Patent

PATENT NO 9864177
SERIAL NO

15230816

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Abstract

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An optical system includes a reflective optical system on a magnification side along an optical path of the projection optical system and a refractive optical system on a reduction side along the optical path. The reflective optical system includes one reflective optical element having a power. The refractive optical system includes a front group on the magnification side and a rear group on the reduction side. The front group having, in order from the magnification side toward the reduction side, a first lens group with a positive or negative refractive power, a second lens group, and a third lens group with a positive refractive power. The rear group has a positive refractive power. The first lens group moves to the magnification side, and the second lens group and the third lens group move to the reduction side in a change in focus from a long distance to a short distance.

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Patent Owner(s)

Patent OwnerAddress
RICOH COMPANY LTDTOKYO

International Classification(s)

Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Shibayama, Yasuyuki Kanagawa, JP 35 295
Takano, Yohei Iwate, JP 53 377
Tatsuno, Hibiki Kanagawa, JP 68 855

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